The extension is not meant to block online ads outright. It’s a broader privacy tool designed to stop third parties from gathering a record of the pages people visit across the Web.

“Our aim is not to block ads, but to prevent non-consensual invasions of people’s privacy because we believe they are inherently objectionable,” the group says.

However, because third-party trackers often exist to serve ads, Privacy Badger users will likely see less of them.

The tool is also designed to stop the tracking that happens when people click on social media widgets such as the Facebook “like” or Twitter tweet button on sites outside of Facebook or Twitter.

Third-party trackers are companies that embed different content like images, scripts and advertising into websites. The companies often use digital files or “cookies” stored in people’s browsers to keep track of their browsing activity. The content these trackers embed on sites often exists alongside the site’s own content, such as news articles on nytimes.com.

Visit a handful of sites and Privacy Badger's sliders quickly go from green to red.

Privacy Badger is designed to keep track of these different sources of content. And if the same source appears to be tracking a person’s browser across different websites, then the extension is meant to stop the tracker from gathering the data.

“This extension is designed to automatically protect your privacy from third-party trackers that load invisibly when you browse the Web,” the EFF says.

Sometimes third-party domains provide content that is necessary for the website to function. In these cases the extension will allow it, but block it from gathering cookies, the EFF says.

The extension uses algorithms to determine whether a domain is tracking a user. Because it’s still in beta, it probably won’t catch them all.

But with its tool, the EFF says it aims to provide something that works automatically without custom configuration.

A built-in browser tool for blocking third-party tracking was conceived years ago by privacy advocates, called “Do Not Track.” The setting is currently in the major browsers, but turning it on doesn’t do much, because many companies don’t honor it.

The EFF said companies blocked by Privacy Badger can unblock themselves by committing to respect people’s Do Not Track requests.

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